Evaluation of Left Anterior Descending Coronary Artery Stenosis of Intermediate Severity Using Transthoracic Coronary Flow Reserve and Dobutamine Stress Echocardiography

Abstract

The physiologic significance of left anterior descending coronary artery (LAD) stenosis of intermediate angiographic severity is of clinical importance and difficult to assess. Assessment of coronary flow reserve (CFR) by Doppler transthoracic echocardiography (TTE) is a new tool and could allow rapid, noninvasive evaluation of stenosis severity in this setting. We sought to evaluate the value of CFR measurement determined by TTE, compared with dobutamine stress echocardiography (DSE), in the setting of LAD stenosis of intermediate angiographic severity. A total of 51 consecutive stable patients in sinus rhythm (33 men; age 65 +/- 12 years; left ventricular ejection fraction 59 +/- 7%) with no previous anterior myocardial infarction and with an angiographic proximal LAD stenosis of intermediate severity (56 +/- 8% quantitative coronary angioplasty) were prospectively studied. Coronary flow velocity was measured in the distal part of the LAD by TTE at rest and during continuous infusion of 0.14 mg/kg/min of adenosine over 2 minutes, using a multifrequency transducer, in the modified parasternal or 3-apical view. CFR was calculated as the ratio of hyperemic to basal mean (mean CFR) and peak (peak CFR) diastolic flow velocity. DSE was performed immediately after the adenosine test to assess ischemia in the LAD territory (percent maximum predicted heart rate = 94 +/- 8). Adequate recording of CFR was possible in 46 patients. Of the 35 patients with a CFR of 2 or more (peak CFR = 2.7 +/- 0.6), DSE was normal in 34. Of the 11 patients with a CFR less than 2 (peak CFR = 1.7 +/- 0.2), 7 had an abnormal response with DSE in the LAD territory. In this range of intermediate stenosis, there was a poor correlation between percent LAD diameter stenosis and CFR. For patients with positive DSE, CFR was 1.6 +/- 0.2 compared with 2.7 +/- 0.6 for patients with normal DSE (P < .05). The sensitivity, specificity, and the positive and negative predictive values of TTE CFR for detecting ischemia on DSE were 88%, 89%, 64%, and 97%, respectively, with an overall agreement of 89% between the two tests. Given its high negative predictive value, noninvasive CFR could be a useful aid in reaching clinical decisions promptly at the bedside in patients with moderately severe lesions of the proximal LAD.